rpc: fix undefined behaviour in __builtin_ctz

Found with GCC UBsan:

rpcsvc.c:102:36: runtime error: passing zero to ctz(), which is not a valid argument
    #0 0x7fcd1ff6faa4 in rpcsvc_get_free_queue_index /path/to/glusterfs/rpc/rpc-lib/src/rpcsvc.c:102
    #1 0x7fcd1ff81e12 in rpcsvc_handle_rpc_call /path/to/glusterfs/rpc/rpc-lib/src/rpcsvc.c:837
    #2 0x7fcd1ff833ad in rpcsvc_notify /path/to/glusterfs/rpc/rpc-lib/src/rpcsvc.c:1000
    #3 0x7fcd1ff8829d in rpc_transport_notify /path/to/glusterfs/rpc/rpc-lib/src/rpc-transport.c:520
    #4 0x7fcd0dd72f16 in socket_event_poll_in_async /path/to/glusterfs/rpc/rpc-transport/socket/src/socket.c:2502
    #5 0x7fcd0dd8986a in gf_async ../../../../libglusterfs/src/glusterfs/async.h:189
    #6 0x7fcd0dd8986a in socket_event_poll_in /path/to/glusterfs/rpc/rpc-transport/socket/src/socket.c:2543
    #7 0x7fcd0dd8986a in socket_event_handler /path/to/glusterfs/rpc/rpc-transport/socket/src/socket.c:2934
    #8 0x7fcd0dd8986a in socket_event_handler /path/to/glusterfs/rpc/rpc-transport/socket/src/socket.c:2854
    #9 0x7fcd2048aff7 in event_dispatch_epoll_handler /path/to/glusterfs/libglusterfs/src/event-epoll.c:640
    #10 0x7fcd2048aff7 in event_dispatch_epoll_worker /path/to/glusterfs/libglusterfs/src/event-epoll.c:751
    ...

Fix, simplify, and prefer 'unsigned long' as underlying bitmap type.

Change-Id: If3f24dfe7bef8bc7a11a679366e219a73caeb9e4
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Fixes: #1283

2 files changed, 19 insertions, 0 deletions

diff --git a/libglusterfs/src/glusterfs/common-utils.h b/libglusterfs/src/glusterfs/common-utils.h
index 69c258d678f..1954cca639f 100644
--- a/libglusterfs/src/glusterfs/common-utils.h
+++ b/libglusterfs/src/glusterfs/common-utils.h
@@ -18,6 +18,7 @@
 #include <string.h>
 #include <assert.h>
 #include <pthread.h>
+#include <unistd.h>
 #include <openssl/md5.h>
 #ifndef GF_BSD_HOST_OS
 #include <alloca.h>
@@ -26,6 +27,11 @@
 #include <fnmatch.h>
 #include <uuid/uuid.h>
 
+/* FreeBSD, etc. */
+#ifndef __BITS_PER_LONG
+#define __BITS_PER_LONG (CHAR_BIT * (sizeof(long)))
+#endif
+
 #ifndef ffsll
 #define ffsll(x) __builtin_ffsll(x)
 #endif
@@ -441,6 +447,15 @@ BIT_VALUE(unsigned char *array, unsigned int index)
     } while (0)
 #endif
 
+/* Compile-time assert, borrowed from Linux kernel. */
+#ifdef HAVE_STATIC_ASSERT
+#define GF_STATIC_ASSERT(expr, ...)                                            \
+    __gf_static_assert(expr, ##__VA_ARGS__, #expr)
+#define __gf_static_assert(expr, msg, ...) _Static_assert(expr, msg)
+#else
+#define GF_STATIC_ASSERT(expr, ...)
+#endif
+
 #define GF_ABORT(msg...)                                                       \
     do {                                                                       \
         gf_msg_callingfn("", GF_LOG_CRITICAL, 0, LG_MSG_ASSERTION_FAILED,      \
diff --git a/libglusterfs/src/glusterfs/gf-event.h b/libglusterfs/src/glusterfs/gf-event.h
index c0f05e7c83b..40f8fbdf10a 100644
--- a/libglusterfs/src/glusterfs/gf-event.h
+++ b/libglusterfs/src/glusterfs/gf-event.h
@@ -12,6 +12,7 @@
 #define _GF_EVENT_H_
 
 #include <pthread.h>
+#include "common-utils.h"
 #include "list.h"
 
 struct event_pool;
@@ -31,6 +32,9 @@ typedef void (*event_handler_t)(int fd, int idx, int gen, void *data,
 #define EVENT_EPOLL_SLOTS 1024
 #define EVENT_MAX_THREADS 1024
 
+/* See rpcsvc.h to check why. */
+GF_STATIC_ASSERT(EVENT_MAX_THREADS % __BITS_PER_LONG == 0);
+
 struct event_pool {
     struct event_ops *ops;